The invention relates to a mechanical gearing with which a fixed or variable transmission ratio can be adjusted between two rotating members.
The invention relates particularly to a mechanical gearing wherein forces are transmitted by friction. A known gearing of this type makes use of two pairs of V-belt pulleys of variable width and a so-called push belt arranged therebetween and comprising abutting links. The construction of the known push belt imposes limitations with respect to the torque that can be transmitted with the gearing.
The present invention has for its object to provide a mechanical gearing of the said type with which a large torque can be transmitted.
This object is achieved in a mechanical gearing as characterized in claim 1. The belt of push links is enclosed all round by the friction bevel gears whereby great forces can be transmitted without the belt being disturbed or damaged. The belt can be in contact over a large angle with both the pair of friction wheels and the single friction wheel so that a large couple can be transmitted.
The gearing according to the invention can be used for adjusting a fixed gearing but can likewise be embodied for adjusting a variable gearing. In this case the steps of claim 2 are applied.
A favourable embodiment is therein characterized in claim 3. When the eccentricity of the shafts is varied the relevant axial distance of the two associated friction wheels is therein adjusted automatically. When the axial distance is increased the two friction wheels of the pair are pressed away from each other and the belt will run at a greater diameter, so that a larger transmission ratio is adjusted from the first to the second shaft.
The mechanical gearing according to the invention can be applied as gearing step in very many different embodiments of mechanical gearings. The gearing according to the invention can in principle be applied in any configuration as tooth wheel transmissions.
A suitable embodiment is therein characterized in claim 4. With gearing steps thus connected in series a very high or low transmission can be adjusted.
A favourable further development is herein characterized in claim 5. It is hereby possible to arrange the input and output shaft of a gearing coaxially, which is desirable in a number of applications.
The gearing according to the invention is preferably equipped with a push belt as characterized in claim 6. Because the push belt is supported over its whole periphery, partly by the friction wheels and partly by the belt engaging wheel, the push belt does not itself have to be able to form a stiff portion as is the case in the known art. By connecting the push links together by pivot shafts the mutual rotation which takes place at the transition from the friction wheels to the belt engaging wheel and vice versa can take place with very little friction, whereby the performance of the gearing is high.
The step of claim 7 is therein preferably applied. The friction hereby becomes extremely low, with the associated positive effect on the performance of the gearing.
The invention will be further elucidated in the following description with reference to the embodiments shown in the figures.